"G.E.L.F." or "GELF" is a term designating any type of Genetically Engineered Life Form in the science fiction sitcom Red Dwarf. The writers of the series had stated early on in production that they did not want any aliens to exist in their show's universe; but as the series continued, in order to provide a stream of characters for the main crew to interact with, their cosmos was gradually populated with deranged robots and bizarre creatures that turned out to be the result of genetic engineering.

Not all of the varieties of GELF are necessarily malevolent, but many are. Some, such as the Polymorphs and Psirens, are manipulative monsters that actively hunt sentient beings. The most common varieties are the "beastmen" types such as the Kinitawowi and Brefewino: aggressive space-barbarians which while capable of piloting spaceships look down on humans as the scum of the universe, to be traded as slaves and sometimes eaten. A few varieties, however, such as the Pleasure GELFs are actually benevolent and non-threatening, though they may have bizarre external appearances.

Gelf-lings should not be confused with the Gelflings of Dark Crystal.

Here are some of the GELFs which have appeared on Red Dwarf over the years, in order of appearance: